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indexOf fails to find the first letter in a string

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  indexOf fails to find the first letter in a string justaguy <lichunshen84@gmail.com> - 2012-09-20 16:25 -0700
    Re: indexOf fails to find the first letter in a string "S.T." <anon@anon.com> - 2012-09-20 17:16 -0700
      Re: indexOf fails to find the first letter in a string justaguy <lichunshen84@gmail.com> - 2012-09-20 18:42 -0700
    Re: indexOf fails to find the first letter in a string Scott Sauyet <scott.sauyet@gmail.com> - 2012-09-20 17:32 -0700
      Re: indexOf fails to find the first letter in a string justaguy <lichunshen84@gmail.com> - 2012-09-20 18:42 -0700
    Re: indexOf fails to find the first letter in a string Dr J R Stockton <reply1237@merlyn.demon.co.uk.invalid> - 2012-09-22 19:18 +0100

#16066 — indexOf fails to find the first letter in a string

Sorry to bug you guys, ran a quick Googling for a solution to no
avail, hence, asking it here.

var str = "$100";
// it would work if we declare the var as
// var str = "100$" but no one writes English like that :)
if (str.IndexOf('$')) {
  alert("Please remove the $ sign");
  return false;
}

What's the correct syntax to do it?  Thanks.

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#16068

On 9/20/2012 4:25 PM, justaguy wrote:
> Sorry to bug you guys, ran a quick Googling for a solution to no
> avail, hence, asking it here.
>
> var str = "$100";
> // it would work if we declare the var as
> // var str = "100$" but no one writes English like that :)
> if (str.IndexOf('$')) {
>    alert("Please remove the $ sign");
>    return false;
> }
>
> What's the correct syntax to do it?  Thanks.

var str = "$100";


if (str.indexOf('$') !=-1) {
   alert("Please remove the $ sign");
   return false;
}

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#16072

On Sep 20, 8:16 pm, "S.T." <a...@anon.com> wrote:
> On 9/20/2012 4:25 PM, justaguy wrote:
>
> > Sorry to bug you guys, ran a quick Googling for a solution to no
> > avail, hence, asking it here.
>
> > var str = "$100";
> > // it would work if we declare the var as
> > // var str = "100$" but no one writes English like that :)
> > if (str.IndexOf('$')) {
> >    alert("Please remove the $ sign");
> >    return false;
> > }
>
> > What's the correct syntax to do it?  Thanks.
>
> var str = "$100";
>
> if (str.indexOf('$') !=-1) {
>    alert("Please remove the $ sign");
>    return false;
>
>
>
>
>
>
>
> }

Thanks.

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#16070

justaguy  wrote:
> var str = "$100";
> if (str.IndexOf('$')) {
          ^^^^^^^

wrong capitalization.  The name is `indexOf`.

>   alert("Please remove the $ sign");
>   return false;
> }

> // it would work if we declare the var as
> // var str = "100$" but no one writes English like that :)

That's because `indexOf` returns an integer, and when in integer is
used where a boolean is expected, as in the `if` statement above, a
zero is read as `false`.  Since the first character of the string has
index 0, the above is interpreted as `if (0)`, or equivalently, `if
(false)`.

A safer solution would be to check

    if (str.indexOf("$") > -1) {
      // ...
    }

  -- Scott

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#16073

On Sep 20, 8:32 pm, Scott Sauyet <scott.sau...@gmail.com> wrote:
> justaguy  wrote:
> > var str = "$100";
> > if (str.IndexOf('$')) {
>
>           ^^^^^^^
>
> wrong capitalization.  The name is `indexOf`.
>
> >   alert("Please remove the $ sign");
> >   return false;
> > }
> > // it would work if we declare the var as
> > // var str = "100$" but no one writes English like that :)
>
> That's because `indexOf` returns an integer, and when in integer is
> used where a boolean is expected, as in the `if` statement above, a
> zero is read as `false`.  Since the first character of the string has
> index 0, the above is interpreted as `if (0)`, or equivalently, `if
> (false)`.
>
> A safer solution would be to check
>
>     if (str.indexOf("$") > -1) {
>       // ...
>     }
>
>   -- Scott

Thanks.  Ooops, typo.

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#16124

In comp.lang.javascript message <7c3f6696-0634-4b17-9ac6-720ca1572e9d@i1
4g2000yqo.googlegroups.com>, Thu, 20 Sep 2012 16:25:08, justaguy
<lichunshen84@gmail.com> posted:

>var str = "$100";
>// it would work if we declare the var as
>// var str = "100$" but no one writes English like that :)
>if (str.IndexOf('$')) {
>  alert("Please remove the $ sign");
>  return false;
>}
>
>What's the correct syntax to do it?  Thanks.


var str = "100";
//  "100$" but no one writes English like that // false comment
if (/\$/.test(str)) {
  alert("Please remove the $ sign");
  // return false;  // not in a function at present
  }


-- 
 (c) John Stockton, nr London, UK.  Mail via homepage.  Turnpike v6.05  MIME.
  Web  <http://www.merlyn.demon.co.uk/> - FAQqish topics, acronyms and links;
  Astro stuff via astron-1.htm, gravity0.htm ; quotings.htm, pascal.htm, etc.
 No Encoding. Quotes before replies. Snip well. Write clearly. Don't Mail News.

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